mac won't delete time machine backups from trash

I'm on a new Mac Studio running Sonoma. My back up drive said it was full so I went into time machine and dragged 6 folders from over a year ago into the trash. I hit empty trash and it was deleting files which took forever but it kept saying some files couldn't be deleted. I tried following a video on how to delete from terminal and that didn't do anything either. I did notice that when i ejected the external hard drive that i use for time machine the trash was empty but as soon as i turned the drive back on the files return to the trash. Any idea what I can do?